Selective oxidation process



Patented Feb. 16, 1954- UNITED STATES PATENT OFFICE SELECTIVE OXIDATION PROCESS William R. Middleton, Wenonah, N. J., assignor to Socony-Vacuum Oil Company, Incorporated, a corporation of New York No Drawing. Original application December 7,

1950, Serial No. 199,719. Divided and this application May 10, 1952, Serial No. 287,261

9 Claims.

The present invention relates to catalysts containing at least one oxide of tellurium and to their use in the catalytic conversion of methyl and methylene groups to carbonyl groups by gas containing free oxygen in the presence of finely divided catalyst comprisin predominantly at least one oxide of tellurium. It is to be understood that the phrase gas containing free oxygen" includes elemental oxygen, pure diatomic oxygen, diatomic oxygen diluted with an inert gas such as nitrogen, helium, carbon dioxide and triatomic oxygen or ozone and air.

In general, as disclosed in the copending application for United States Letters Patent Serial No.'139,529, filed January 19, 1950, in the name of Frederick P. Richter, the method of converting methyl or methylene groups to carbonyl groups involves contacting the vapors of an organic substance having hydrogen atoms activated by the proximity of a double bond; i. e., alpha to an unsaturated carbon atom, or a hydroxyl group with a gas containing free oxygen in the presence of finely divided catalyst comprising predominantly at least one oxide of tellurium to obtain a compound containing a carbonyl group.

Richter, in the aforesaid copending application Serial No. 139,529, has stated that broadly illustrative of the classes of compounds which can be oxidized in this manner and the products obtained are the following equations:

0 ll 0 g .uocn, A1 CHO +1120 where Ar is an aryl radical substituted or unsubstituted.

o (2 (a) n'oniornon T R(-0HO+2H:0

o (b) RCHOHCHzOH R'COCHO+2H:O

6 where R is hydrogen, alkyl, cycloalkyl, aryl,

heterocyclic and where other than hydrogen may be substituted by any substituent which will survive under the reaction conditions, for example. a phenyl group, a halogen, 2. nitro group, and the like.

It will be recognized that in the foregoing Z represents HC=C-; H2C=CH-; Ar-; ArC=-O-; R'CH2-; R'CHOH; and R0H-.

(3) Compounds containing a centerof unsaturation directly adjacent to a methyl or methylene group such as the double bond of an aryl group as an integral part of an alicyclic ring system:

has been used in the foregoing equations to indicate a reaction taking place in the presence of a gas containing free oxygen as defined hereinbefore and a finely divided catalyst comprising predominantly at least one oxide of tellurium.

The manner in which the finely divided catalyst comprising at least one oxide of tellurium is used apparently is unimportant. For example, it can be used as a finely divided, unsupported catalyst, or as a finely divided catalyst on an inert support or an active support. lt is to be noted An organic carmary or secondary alcohol and a carboxylic acid. An inert support is one which in the absence of catalyst comprising predominantly atleast one oxide or tellurium but in the presence of a gas containing free oxygen does any appreciable extent the oxidation of organic substances of the class described hereinbefore to produce oxidation products.

The present invention provides an improvement of the invention the copending application from which a portion of the foregoing has been taken. Accordingly, the improved catalyst and the improved metnod described hereinafter is co-extensive in scope with that or application Serial No. 139,529; that is to say, the improved catalyst is useful in the oxidation of propylene to-acrolein, in the oxidation of a mixture ofrefinery gases suclras a propylene-propane fraction, in the oxidation of isobutylene to methacrolein, and in the oxidation of toluene to benzaldehyde as described in the-copending application Serial No. 139,529.

While the unpromoted catalysts comprising predominantly at least one oxide of tellurium can be supported or unsupported, and the unpromoted catalyst can be prepared by mechanical sub-division of the metal, technical difficulties are encountered when an attempt is madeto prepare the promotedv catalysts by mechanical sub-division. Therefore, it is preferred to prepare thepromoted catalysts'containing at least one oxide of tellurium and a critical minimum concentration of a promoter oxide by methods other than mechanical sub-division.

There is evidence that the tellurium catalyst is a labile system of metallic tellurium and at least one oxide of tellurium but evidence is lacking regarding how the promoter affects this system.

It is preferred to employ a supported catalyst, i. e., to distribute the promoted catalyst over a supporting material which may be of the inert type or of the active type. Inert supports are those such as fused alumina which per se do not accelerate oxidation reactions. Active supports are those which, like silica gel, per se accelerate the oxidation of olefins to C0, C02, andI-IzO.

While the catalyst and'method disclosed in copending application Serial No. 139,529 have provided satisfactory results in the oxidation of methyl or methylene groups to carbonyl groups, it has been found that even these" satisfactory results can be improved. For example, when using a supported catalystsuch as described in Serial No. 139,529. having theinert fused alumina support, very low space velocities, such as 0.3 to 0.5, were necessary to obtain the best conversions of to 8%. Higher. space velocities lead to a sharp reduction in the conversion when. the catalyst is the unpromoted catalyst of application Serial No. 139,529. On the other hand,, when supported catalysts having active supports such those of the carbonyl exists-in that'state of oxidation which is intermediate between a prinot accelerate to described and defined in 0 Serial No. 139,529,

having inert supports. having active supports, the conversion per pass was greater under favorable conditions and space bustion-occurred. These diificulties resulted in much lower ultimate conversions to carbonyl products when using unpromoted catalysts having active supports compared with the ultimate conversions employing inert supports. The ultimate conversions with catalysts having active supports in some instances were only about 36 toabout 66% of those obtained with catalysts However, withv catalysts velocities could be increased from 0.3 to 0.5 to into 2.0 without excessive drop in conversion per pass.

96, permits the use of higher spacevelocities at equal or greater conversions per pass without substantial loss in ultimate conversion or yield.

It is to be noted that catalysts which, at least theoretically, contain the promoter as a tellurate are not equivalent to the promoted catalysts of the present invention wherein the promoterv as well as the tellurium is present predominantly as at least one oxide. the foregoing is manifest from thefollowing facts.

Two tellurium catalysts were prepared con-- taining the equivalent of 25 mole per centuranium oxide. In catalystA the mixed oxides were prepared by steamhydrolysis of the-mixedoxychlorides. In catalyst B the uranium was incorporated: as uranyltcllurate in three moles of. excess telluric acid. The excess telluric acidwas dehydrated and reduced. readily under catalyst operating conditions to tellurium oxide. The two catalysts A and B were evaluated at 752-'754 F. for the conversion" of propyleneto acrolein using a molar air-to-propylene ratio of 3.0 and a gas space velocity of 40 42 with each catalyst. The conversion of propylene't'o acrolein with'ca'talyst A containing the'promoter asan oxide-was 937% while the'conversion of propylene to acrolein with catalyst 13, wherein the promoter was not present as an oxide, was only 4.9%, i. e., of the order obtainedwith the'un'promoted catalysts described mixed catalysts contain about 1 to about 40- more per cent; preferablyabout 5 to about35 mole'per cent, based upon the tellurium of a metal of Group VI having an atomic weight of at least about96, said metalbeing in the formof at least one oxide and not as a' compound of tellurium. Accordingly, the novel catalysts are supported or unsupported mixtures predominantly of about 1 to about 4'0 mole per cent, preferably about 5 to about 35 mole per cent, based upon the tellurium of at least one oxide of a metal of Group VI having anatomic weight ofat'least about 96, i. e., molybdenum, tungsten and uranium, and the balance predominantlyat least one oxide of tellurium.

The supported catalysts can have as supports either an inert material or an active material as defined hereinbefore and in copending application Serial No. 139,529.

It is preferred to prepare the supported catalysts in the following ways:

PROCEDURE A A supporting material, either of the inert type or of the active type, i. e., say fused alumina or silica gel, is saturated with a concentrated aqueous solution of telluric acid and the amount of a suitable promoter precursor sufficient to give between about 1 and about 40, preferably between about 5 and about 35 mole per cent of the promoter oxide based upon the tellurium. The promoter precursor is a compound of the promoter metal containing no other metallic component and capable of being converted to the oxide if not then in the form of the oxide. For example, 85 per cent molybdic acid, uranyl nitrate or acetate, and tungsten chloride can be used. Thus, when preparing a molybdenum promoted catalyst, that amount of 85 per cent molybdic acid necessary to yield about 5 to about 40 mole per cent molybdic oxide is dissolved in an aqueous solution of telluric acid and the support saturated with the telluric acid solution.

PROCEDURE B A solution of tellurium dioxide and, say, an amount of uranyl nitrate sufiicient to yield uranium oxide equivalent to about 5 to about 40 mole per cent of the tellurium dioxide, is prepared in concentrated (38-39%) hydrochloric acid. The solution so obtained is adjusted by dilution or evaporation, as necessary, to just saturate the pores of the support to which it is to be applied. Upon drying the saturated support, an oxychloride coating is obtained upon the support. The coated support is then placed in a suitable container and the oxychloride coating hydrolyzed with steam at about 420-675 F. for a suitable period of up to about 30 hours. Hydrolysis to the oxide form is complete when the steam condensate no longer gives a positive test for the chloride ion. Thereafter, residual steam is flushed from the catalyst with dry air or oxygen and the catalyst is ready for use.

The preferred support for the promoted or mixed catalysts described herein is 8-14 mesh inert, fused alumina known as tabular alumina. This inert alumina exhibits a porosity in the range of about 15 to about 25 per cent and a surface area in the range of about 3-5 square meters per gram. In the illustrative but not limiting examples given hereinafter, the concentration of tellurium oxide (as TeOz) upon the tabular alumina was either about 10 or about grams per 100 cubic centimeters of the alumina support. However, no significant difierence was noted, in performance of these catalysts which could be attributed to the variation in the concentration of tellurium oxide on the support.

It is to be noted that specific, selective partial oxidation of the compounds discussed hereinbefore in the presence of these tellurium catalysts produces a moderate amount of heat whereas complete unselective oxidation of an appreciable percentage of the compound charged to the catalyst zone is accompanied by the evolution of an excessive amount of heat. In other words, when these compounds are oxidized to carbonyl compounds, the reaction produces a moderate amount of heat in the catalyst zone which is readily dissipated and controlled. In general, in the operation of tellurium catalysts which are highly selective in their action, there is a rise of less than about one degree Fahrenheit for each mole per cent of compound converted to the carbonyl. In contrast, tellurium catalysts which are low in selectivity, i. e., performing complete as well as partial oxidations, are subject under similar conditions to temperature rises in the catalyst bed of 5-10 F. per mole per cent of compound converted to carbonyl.

In the following illustrative but not limiting examples of the improved method for converting methyl and methylene groups activated by the proximity of a center of unsaturation, or a carbonyl group, to a carbonyl group with a gas containing free oxygen in the presence of a catalyst comprising about 5-35 mole per cent of an oxide of a metal of Group VI having a molecular weight of at least about 96 and the balance predominantly at least one oxide of tellurium, reference is made to the maximum observed temperature rise in the catalyst due to the oxidation reactions which is indicative of the degree of selectivity exhibited by the cataly t.

Example I A gaseous mixture of propylene and'air in the proportion of one volume of propylene to 3 volumes of air was passed at essentially atmospheric pressure through one volume of catalyst at the rate of 4 volumes of the gaseous mixture per minute or at a space velocity of 4 equivalent to a propylene space velocity of 1. The temperature of the reaction zone was maintained at about '750-75i F. The maximum observed temperature rise in the catalyst due to oxidation was 4 1". The catalyst was prepared in accordance with Procedure 13 given hereinbefore and contained 0.05 mole of U03 based upon the tellurium.

The product was absorbed in water at a temperature below 50 F. Analysis of the aqueous solution indicated that about 4.5 per cent of the propylene was converted to acrolein.

Under the same conditions, a tellurium catalyst such as described in copending application Serial No. 139,529, gave a conversion of only about 1.8 per cent of the propylene to acrolein.

Example II A gaseous mixture of propylene and air in the proportion of one volume of propylene to two volumes of air was passed at essentially atmospheric pressure through one volume of catalyst at the rate of three volumes of the gaseous mixture per minute or at a space velocity of 3 equivalent to a propylene space velocity of 1. The maximum observed temperature rise in the catalyst due to the oxidation reaction was 14 F. and the temperature of the reaction zone was maintained at about 742-756 The catalyst was prepared in accordance with Procedure 13 given hereinbefore and the catalyst contained 0.25 mole of U0: per mole of tellurium oxide or 25 mole per cent of U03 based on the tellurium oxide.

Analysis of the aqueous solution obtained by absorption of the product in water at a temperature below about 50 F. indicated that about 15.2 per cent of the propylene was converted to acro-. lein. An independent analysis of the total gases from the reaction zone by means of a mass spectrometer indicated that about 20.0 per cent of the propylene was converted to acrolein and about 5.2 per cent was converted to carbon monoxide and carbon dioxide.

Under the same conditions, a catalyst containing an equivalent amount of tellurium oxide gave a conversion of only about 1.4 percent of wherein and R are alkyl or aryl groups substituted or unsubstituted can be oxidized in the manner described hereinbefore and converted to the corresponding carbonyl compounds.

Thus, for example, 1,3-butadiene, l,3-penta-- diene (alphamethylbutadiene) Le-pentadiene, 2-methyl-l,3-butadiene (isoprene), 1,5hexadiene (diallyl), Z-methyl-lA-pentadiene (isodiallyl), 2,3-dimethyl-1,3-butadiene (diisopropenyl), 3-methyl-1,3-hexadiene, 3-methyl2, hexadiene, 2,7-heptadiene, 4-methyl-1,6-heptadiene, 2,5-dimethyl-2,4-hexadiene, 3-methyll,5- octadiene, 1,4-nonadiene, 3,7-decadiene can be oxidized with air in the presence of finely divided catalyst comprising predominantly at least one oxide of tellurium at temperatures of about 350 to about 550 C. or generally at temperatures at which the diolefin is gaseous but below the cracking temperature of the diolefin, to the corresponding carbonyl compounds.

Illustrative of another group of hydrocarbons which can be oxidized to the corresponding carbonyl compounds in gaseous phase with pure or diluted gaseous oxygen in the presence of the tellurium catalyst at temperatures at which the hydrocarbon is gaseous but below the cracking temperature of the hydrocarbon are the following members of the acetylene series: 2-butyne, Z-pentyne, 2-hexyne, 3-hexyne, 4-methyl-2-pentyne, B-heptyne, 5-methyl-2- hexyne, 4,4dimethyl2-pentyne, 5-methyl-5- ethyl-S-heptyne, 2-undecyne, G-dodecyne, 2- hexadecyne, 9-octadecyne.

Illustrative of the aromatic hydrocarbons which can be oxidized to the corresponding carbonyl compounds by air in the presence of the "tellurium catalyst at temperatures between the normal boiling point of the hydrocarbon and the cracking temperature thereof are trimethylbenzene, o-ethyltoluene (l-methyl2-ethylbenzene) l-methyl-2-propylbenzene, 1,3-dimethyl- 4-ethylbenzene, tetra-methylbenzene, l-methyld-isobutylbenzene, 1,2-dimethyl 4 propylbenzene, 1,2,4-trimethyl-5-ethylbenzene, 1-methyl- 3-amylbenzene, 1,3-dimethyl-i,G-diethylbenzene, 1-methy1-2propyl4-isopropylbenzene, 1,3,5-trlmethyl-2,-diethylbenzene, alpha and beta styrene, 1-phenyl-1,3-butadiene, l-methyl-elpropenylbenzene, 1-phenyl-2-pentene, dimethyl naphthalene, dimethylanthracene, dimethylphenanthrene, and the like.

Illustrative of the cyclo-olefins which can be oxidized to the corresponding carbonyl compounds by air in the presence of the tellurium catalyst at temperatures between the boiling point and the cracking temperature of the cycloolefin are l-methyl-l-cyclobutene, 1-methyllcyclopentene, 1,2 dimethyl 1 cyclopentene, 1-methyl-2-ethyl-1-cyclopentene, 1 methyl-2- propyl l cyclopentene, 1,2-dimethyl-l-cyclohexene, and 1-ethyl-3-methyl-1-cyclohexene.

Illustrative of the organic compounds having a methyl or methylene group activated by the presence of a hydroxyl group, which can be oxidized to the corresponding carbonyl compounds by gaseous oxygen (pure or diluted), ozone, and air in the presence of the tellurium catalyst at temperatures between the boiling point of the compound and the temperature at which said compound cracks or decomposes, are

the following: glycol, propandio1-1,2; propandiol-1,3; 1,2-dihydroxybutane, 1,4-clihydroxybutane, 2,3-dihydroxyhexane, and the like. Monohydroxy compounds such as the aliphatic alcohols, ethanol, butanol, propanol, hexanol, octanol, and the like can also be oxidized to the corresponding carbonyl compounds by gaseous oxygen in the presence of the tellur catalyst at temperatures between the boiling point of the alcohol and the temperature at which the alcohol decomposes.

A characteristic of the catalyst disclosed here inbefore is its capacity to promote the oxidation of methyl or methylene groups directly adjacent to a center of unsaturation in an organic .compound such as, for example, the unsaturation found in aromatic compounds, olefins or carbonyl groups. A further distinguishing feature is the fact that although the catalyst catalyzes the oxidation of such methyl and methylene groups to carbonyl groups, =C=O or it does not catalyze the oxidation of carbonyl groups to higher states of oxidation. Thus, it is specific for the following transformations:

ARCHZR ARCR be oxidized to glyoxal and anthracene to anthraquinone, as can organic substances which form in situ reactants such as those the oxidation of which has been discussed herein or their intermediate oxidation products through dehydrogenation, dehydration, rearrangement, dehalogenation, dehydrohalogenation and similar reactions, for instance, methyl cyclohexadiene, tertiary butanol, beta-pinene, 2,3-diiodopropane and alpha-bromodiethylketone.

This application is a division of copending application Serial No. 199,719, filed December 7, 1950.

I claim:

1. In the method of oxidizing compounds having a radical selected from the group consisting of methyl and methylene radicals adjacent to an activating moiety selected from the group consisting of a center of unsaturation and a carbonyl group to convert said radical to a carbonyl group which comprises heating a compound having a group selected from the groups methyl and methylene adjacent to an activating moiety selected from the group consisting of a center of unsaturation and a carbonyl group in admixture with a gas containing free oxygen in the presence of a catalyst consisting predominantly of an oxide of tellurium to a temperature between the boiling point of said compound and the temperature at which said compound decomposes, the improvement which comprises employing a catalyst consisting essentially of about 1 to about 49 mole per cent of an oxide of metal of Group VI of the periodic table having an atomic unsaturation, organic substanceshayiu ga methyl group adj acent-tb a carbonylgroup and organic perature of decomposition of-saidwraanic sub-,,

at hvwntwhbh comprises empl y n awtflist-cs ps tieeemia l f-= a u 5-136 about 3 5 rnoleaper cent of ar oxide of-a metal of Group VI oftfia periodic table -having anatomic weight of at 1e st-about-Qdandan-oxide of tellurium.

3. The invention as described and set forth in claim 1, wherein the reaction temperature is about; 600 E. tp-ahout mqtm .4- he: e ti nasrde qrihed andrse r pxthj in; claim 1, wherein the v about 700 F. to about 800 F.

5. The invention; as described and set forth in claim 2, wherein the reactiorr temperai i reis about 600 F. to about 900 F.

6. The invention as set forth and described in claim 2, wherein the reaction temperature is about 700 F. to about 800 F.

per cent of an oxlde of a rne adjacent to an activatinggroup selected from a center of unsaturation and a carbonyl group her by, sai ad ca s s vely, o di d to carb n l; emu? hom rise q nasais x a liqeqmpeimd.imhe v q t a i h f ga containingjree oxygen intl're presence qI-=a cat; 1ytc9n$i nae$ itiallx ran'q d q i lutin weapon? 9 a ou qm r e n h a Ox de q a x eta lqqte giltom h unqon i in mplyb emlml y g t naadu fin.

P o ess s esq h qmno set mm, n. aim? whe e b l e a ysiu on ui es ntiall ia x d o llut m. ndzabqutfz. .a outrfl 3 1a. c r ain? cq s sti e essentia li oifiaah psriqdiqfiable ha m' an tom lehwiisat least about 96'.

' @PWQNY Refe en es.Qitedtiat a leeqtith anatena UNITEDrSTATESwPA'BENTS 

1. IN THE METHOD OF OXIDIZING COMPOUNDS HAVING A RADICAL SELECTED FROM THE GROUP CONSISTING OF METHYL AND METHYLENE RADICALS ADJACENT TO AN ACTIVATING MOIETY SELECTED FROM THE GROUP CONSISTING OF A CENTER OF UNSATURATION AND A CARBONYL GROUP TO CONVERT SAID RADICAL TO A CARBONYL GROUP WHICH COMPRISES HEATING A COMPOUND HAVING A GROUP SELECTED FROM THE GROUPS METHYL AND METHYLENE ADJACENT TO AN ACTIVATING MOIETY SELECTED FROM THE GROUP CONSISTING OF A CENTER OF UNSATURATION AND A CARBONYL GROUP IN ADMIXTURE WITH A GAS CONTAINING FREE OXYGEN IN THE PRESENCE OF A CATALYST CONSISTING PREDOMINANTLY OF AN OXIDE OF TELLURIUM TO A TEMPERATURE BETWEEN THE BOILING POINT OF SAID COMPOUND AND THE TEMPERATURE AT WHICH SAID COMPOUND DECOMPOSES, THE IMPROVEMENT WHICH COMPRISES EMPLOYING A CATALYST CONSISTING ESSENTIALLY OF ABOUT 1 TO ABOUT 40 MOLE PER CENT OF AN OXIDE OF METAL OF GROUP VI OF THE PERIODIC TABLE HAVING AN ATOMIC WEIGHT OF AT LEAST BOUT 96 AND AN OXIDE OF TELLURIUM. 